feat(i18n): default the cn build to Chinese

The .cn site exists for Chinese readers, so the unprefixed routes should
serve Chinese there. Rspress omits the prefix for the default locale, so
this also moves the routes:

              .com                      .cn
  English     /                         /en-gb/
  Chinese     /zh-hans/                 /

- Make the default locale a per-target value rather than a constant, and
  move the localePrefix helper inside createConfig so a prefix can no
  longer be hardcoded elsewhere.
- Build the sitemap priority map from localePrefix. The keys are full
  route paths, so the previous hardcoded "/zh-hans/..." entries would
  have silently stopped matching on .cn.
- Widen the nav Home activeMatch to cover either prefixed home, since the
  two targets put a different locale behind the prefix.

Note: README.md also carries the licence wording changed in the next
commit — a single file's hunks cannot be split non-interactively.

rspress.config.ts

@@ -22,13 +22,44 @@ const ORIGINS: Record<SiteTarget, string> = {
   cn: "https://onixbyte.cn",
 }
 
-/** Locale used for the unprefixed routes. */
-const DEFAULT_LANG = "en-gb"
+/** Every locale the site is published in, default first for each target. */
+const LANGS = ["en-gb", "zh-hans"] as const
+
+/**
+ * Locale served from the unprefixed routes.
+ *
+ * `.com` leads with English; `.cn` leads with Chinese, so a visitor landing on
+ * the bare domain gets the language that site exists for. The other locale then
+ * moves to a prefix — on `.cn`, English lives at `/en-gb/`.
+ */
+const DEFAULT_LANG: Record<SiteTarget, string> = {
+  com: "en-gb",
+  cn: "zh-hans",
+}
 
 /** hreflang and Open Graph locale codes, keyed by Rspress lang. */
 const HREFLANG: Record<string, string> = { "en-gb": "en-GB", "zh-hans": "zh-Hans" }
 const OG_LOCALE: Record<string, string> = { "en-gb": "en_GB", "zh-hans": "zh_CN" }
 
+/** Language-switcher labels, keyed by Rspress lang. */
+const LOCALE_LABELS: Record<string, string> = {
+  "en-gb": "English (Great Britain)",
+  "zh-hans": "简体中文",
+}
+
+/** Site title and description, keyed by Rspress lang. */
+const LOCALE_META: Record<string, { title: string; description: string }> = {
+  "en-gb": {
+    title: "OnixByte",
+    description:
+      "OnixByte builds self-developed SaaS products and delivers custom software engineering services.",
+  },
+  "zh-hans": {
+    title: "OnixByte",
+    description: "曜珀科技自主研发 SaaS 产品，并提供定制化软件开发服务。",
+  },
+}
+
 /**
  * Social links, split by whether they are reliably reachable from mainland
  * China. The `.cn` build renders only the `domestic` set.
@@ -73,19 +104,31 @@ const SOCIAL_LINKS: Record<"domestic" | "international", SocialLink[]> = {
 type CustomMapsOption = NonNullable<Parameters<typeof pluginSitemap>[0]["customMaps"]>
 type SitemapOverrides = Record<string, Omit<CustomMapsOption[string], "loc">>
 
-const SITEMAP_PRIORITIES = {
-  "/products/": { priority: "1.0" },
-  "/zh-hans/products/": { priority: "1.0" },
-  "/services/": { priority: "1.0" },
-  "/zh-hans/services/": { priority: "1.0" },
-  "/opensource-projects/": { priority: "0.8" },
-  "/zh-hans/opensource-projects/": { priority: "0.8" },
-} satisfies SitemapOverrides
+const PRIORITISED_ROUTES = [
+  ["/products/", "1.0"],
+  ["/services/", "1.0"],
+  ["/opensource-projects/", "0.8"],
+] as const
 
-const localePrefix = (lang: string) => (lang === DEFAULT_LANG ? "" : `/${lang}`)
+/**
+ * Builds the override map for a target.
+ *
+ * The keys are full route paths, so they depend on which locale is unprefixed —
+ * `/products/` means English on `.com` and Chinese on `.cn`.
+ */
+function sitemapPriorities(localePrefix: (lang: string) => string): SitemapOverrides {
+  return Object.fromEntries(
+    LANGS.flatMap((lang) =>
+      PRIORITISED_ROUTES.map(([routePath, priority]) => [
+        `${localePrefix(lang)}${routePath}`,
+        { priority },
+      ])
+    )
+  ) satisfies SitemapOverrides
+}
 
 /** Strips the language prefix, always returning a leading slash. */
-function bareRoutePath(routePath: string, lang: string): string {
+function bareRoutePath(localePrefix: (lang: string) => string, routePath: string, lang: string) {
   const prefix = localePrefix(lang)
   const rest = prefix && routePath.startsWith(prefix) ? routePath.slice(prefix.length) : routePath
   return rest.startsWith("/") ? rest : `/${rest}`
@@ -112,16 +155,19 @@ function pluginRobots(origin: string): RspressPlugin {
 
 export function createConfig(target: SiteTarget): UserConfig {
   const origin = ORIGINS[target]
+  const defaultLang = DEFAULT_LANG[target]
   const socialLinks = [
     ...SOCIAL_LINKS.domestic,
     ...(target === "cn" ? [] : SOCIAL_LINKS.international),
   ]
 
+  /** Rspress drops the prefix from the default locale's routes. */
+  const localePrefix = (lang: string) => (lang === defaultLang ? "" : `/${lang}`)
+
   return defineConfig({
     root: path.join(__dirname, "docs"),
-    title: "OnixByte",
-    description:
-      "OnixByte builds self-developed SaaS products and delivers custom software engineering services.",
+    title: LOCALE_META[defaultLang].title,
+    description: LOCALE_META[defaultLang].description,
     icon: "/onixbyte-icon.svg",
     logo: {
       light: "/onixbyte-light-logo.svg",
@@ -139,8 +185,8 @@ export function createConfig(target: SiteTarget): UserConfig {
     head: [
       (route) => {
         const canonical = `${origin}${route.routePath}`
-        const bare = bareRoutePath(route.routePath, route.lang)
-        const otherLang = route.lang === DEFAULT_LANG ? "zh-hans" : DEFAULT_LANG
+        const bare = bareRoutePath(localePrefix, route.routePath, route.lang)
+        const otherLang = LANGS.find((lang) => lang !== route.lang) ?? route.lang
         const alternate = `${origin}${localePrefix(otherLang)}${bare === "/" ? "/" : bare}`
         const defaultUrl = `${origin}${bare === "/" ? "/" : bare}`
 
@@ -172,22 +218,13 @@ export function createConfig(target: SiteTarget): UserConfig {
     markdown: {
       showLineNumbers: true,
     },
-    lang: DEFAULT_LANG,
-    locales: [
-      {
-        lang: "en-gb",
-        label: "English (Great Britain)",
-        title: "OnixByte",
-        description:
-          "OnixByte builds self-developed SaaS products and delivers custom software engineering services.",
-      },
-      {
-        lang: "zh-hans",
-        label: "简体中文",
-        title: "OnixByte",
-        description: "曜珀科技自主研发 SaaS 产品，并提供定制化软件开发服务。",
-      },
-    ],
+    lang: defaultLang,
+    // The default locale is listed first so the language switcher leads with it.
+    locales: [defaultLang, ...LANGS.filter((lang) => lang !== defaultLang)].map((lang) => ({
+      lang,
+      label: LOCALE_LABELS[lang],
+      ...LOCALE_META[lang],
+    })),
     // Local full-text search. This is already the Rspress v2 default; stated
     // explicitly so the intent is visible. The index is emitted per locale to
     // `static/search_index.<lang>.<hash>.json` at build time.
@@ -200,12 +237,10 @@ export function createConfig(target: SiteTarget): UserConfig {
         siteUrl: origin,
         defaultChangeFreq: "weekly",
         defaultPriority: "0.5",
-        // Keys are full route paths, so the non-default locale needs its own
-        // entries — `/products/` does not match `/zh-hans/products/`.
         // Double assertion rather than a plain cast: the plugin's `Sitemap` type
         // requires `loc`, so the two types do not overlap enough for a single
-        // assertion. See `SITEMAP_PRIORITIES` above for why omitting it is right.
-        customMaps: SITEMAP_PRIORITIES as unknown as CustomMapsOption,
+        // assertion. See `sitemapPriorities` above for why omitting it is right.
+        customMaps: sitemapPriorities(localePrefix) as unknown as CustomMapsOption,
       }),
       pluginRobots(origin),
     ],